Due to sch characteristics as thinness, light weight, and high picture quality, a liquid crystal display device can compete with a cathode ray tube (CRT) as a display device. Various addressing modes of the liquid crystal display device include a twisted nematic (TN) type, a super twisted nematic (STN) type, a ferroelectric liquid crystal (FLC) type, antiferroelectric liquid crystal (AFLC) type, or a polymer dispersion type. A liquid crystal display device with multicolor and high definition is commercially sold.
With the growing demand for a large area display and excellent viewing characteristics, an enlarging projection type display device is increasingly desired.
Most of the liquid crystal display devices mainly use the TN or STN as the addressing mode. However, such addressing modes have the drawback that the display quality changes depending upon the angle of the observation. Polymer dispersed type liquid crystal display devices, which are increasingly desired due to production ease and display brightness (achieved as a result of not using a polarizing plate), have the same problem.
In general, since these liquid crystal display devices are designed so as to provide best display quality when observed along the normal to the display plane, the display quality deteriorates as the angle made between the normal to the display plane and the observation direction becomes larger. That is, these devices disadvantageously have a narrow satisfactory angle of view.
Attempts to widen the satisfactory viewing angle of the liquid crystal display include methods for expanding the angle range to which a light beams having good display quality can be provided such as setting an optical element such as a microlens-array on a liquid crystal display device at the side from which the device is observed.
Examples of such methods include: a method of mounting a light guiding plate and a scattering plate as disclosed in the Japanese Patent Publication Laid Open (Kokai) Hei No. 5-196927; a method of mounting two sheets of orthogonally arranged unidimensional microlens-array as disclosed in the Japanese Patent Application Laid Open (Kokai) Hei No. 7-43704; a method of mounting a transparent plate having transparent micro beads arranged thereon in high density as disclosed in the Japanese Patent Application Laid Open Kokai) Hei No. 7-72469; a method of mounting a material prepared by thinly slicing a bundle consisting of many optical fibers as disclosed in the U.S. Pat. No. 5,329,386; and a method of arranging a lens on each display unit of a liquid crystal cell as disclosed in the Japanese Patent Applications Laid Open (Kokai) Sho No. 62-56930, Hei No. 2-108093, and Hei No. 6-230358.
However, aforementioned production methods of a microlens-array have problems. That is, since they require strict control of the structure, such as the prerequisite that the production technology be able to make micro beads having a uniform diameter (as disclosed in the Japanese patent Applications Laid Open (Kokai) Hei Nos. 5-196927 and 7-72469) and the necessity of a lithography process, the number of production process steps should increase. Moreover, as to the method of arranging a lens on each display unit of the liquid crystal cell, the production process inevitably becomes difficult since the method requires the strict control of the position and size of the display unit and the lens in order to realize its sufficient effect.